These are the rules for normal people..

Inheritance Tax

is a tax on the estate (the property, money and possessions) of someone who’s died.

There’s normally no Inheritance Tax to pay if either:

• the value of your estate is below the £325,000 threshold
• you leave everything above the £325,000 threshold to your spouse, civil partner, a charity or a community amateur sports club

The standard Inheritance Tax rate is 40%. It’s only charged on the part of your estate that’s above the threshold.

https://www.gov.uk/inheritance-tax

Business Relief for Inheritance Tax

What qualifies for Business Relief

You can get 100% Business Relief on:

• a business or interest in a business
• shares in an unlisted company

You can get 50% Business Relief on:

• shares controlling more than 50% of the voting rights in a listed company
• land, buildings or machinery owned by the deceased and used in a business they were a partner in or controlled
• land, buildings or machinery used in the business and held in a trust that it has the right to benefit from

You can only get relief if the deceased owned the business or asset for at least 2 years before they died.

https://www.gov.uk/business-relief-inheritance-tax/what-qualifies-for-business-relief